Extracts of foliar fungal endophytes of Picea glauca and P. rubens (white and red spruce) have been shown to be antifungal and toxic to insects when incorporated into diets (Sumarah et al., 2008b, 2010; Sumarah and Miller, 2009). It has been demonstrated that seedlings can be inoculated with these endophytes and that their metabolites accumulate in the needles, providing the tree with tolerance against spruce budworm (Miller et al., 2008; Sumarah et al., 2008a). Cronartium ribicola (white pine blister rust) is an introduced disease found in all five needle pines in North America. This disease has caused massive economic loss especially in eastern white pine because of the broad range of this species. It has affected Pinus monticola (western white pine) to the point where it is no longer a viable commercial species in many regions of British Columbia, Canada. Natural populations of Pinus are highly susceptible to this disease. After these experiments were initiated, various species of Pinus have been shown to harbour endophytes (Ganley et al., 2008).